JP 2008-274885 A discloses a configuration that has an exhaust heat recovery system provided in an exhaust passage to recover heat of an exhaust gas to a coolant by internally flowing the coolant passing through an internal combustion engine. In addition, JP 2008-274885 A discloses a control selecting a higher value out of a coolant flow rate necessary to prevent boiling of the coolant inside an internal combustion engine and a coolant flow rate necessary to prevent boiling of the coolant inside an exhaust heat recovery system, and using the selected value as a flow rate of the coolant circulating inside a cooling system.
Meanwhile, JP 2007-218115 A discloses a control in which a coolant flow rate is restricted at the start of the internal combustion engine (zero flow control), and the restriction of the coolant flow rate is released as the coolant temperature at an outlet duct of the engine reaches a valve open temperature of an automatic temperature controller. In the control disclosed in JP 2007-218115 A, the coolant flow rate passing through the internal combustion engine is restricted at the engine start, so that a heat amount dissipated to the coolant from the internal combustion engine is restricted. Therefore, it is possible to shorten a time period until the internal combustion engine is warmed up (warm-up time). In addition, the restriction of the coolant flow rate is released as the coolant temperature reaches the valve open temperature of the automatic temperature controller, so that it is possible to prevent boiling of the coolant.